The present invention relates to an arrangement for surveillance of and the possibility of action in, a large geographical area.
Over a large geographical area--a border area, a province, a coastline, a large road network, an urban area etc., there is often a need to watch over and monitor certain defined phenomena which are observable using chemical or physical measuring methods. The phenomena can for example be detected with the aid of the signals which the phenomena generate/emit. The phenomena may be rain fronts, pollution, illegal intrusion of people, vehicles, boats, aircraft or helicopters and the signals may for example be acoustic, chemical, optical or electromagnetic.
The meteorological service forms an idea about rain fronts nowadays with information from different types of satellite, weather radar, manual observations etc. These methods cover the entire country but cannot give any immediate information on how much rain actually falls in individual places and with what intensity.
In this respect, it emerges that, even with complicated equipment, these cannot provide all the answers the meteorological service and the public, and particularly farmers, want to receive. Regional road administration bodies and local authorities also have a great need to be forewarned about rainfall of great intensity.
Air pollution is an increasingly important matter for everyone and nevertheless there is only a small number of permanent measuring stations in the country around inter alia nuclear power stations. Most measurements of air pollution which take place appear to be carried out by a small number of expensive and complicated mobile measuring stations.
As a result of the fact that use is made of a small number of mobile measuring stations, these cannot of course be in the "right" place to discover new air pollution, nor can these few measuring stations follow and indicate the spread of any air pollution.
Illegal intrusion sometimes consists of only intrusion of signals or a combination of physical intrusion and intrusion of signals. An example of such a phenomenon is reconnaissance radar. It is of course desirable to repel an undesirable reconnaissance radar together with its radar signals. If it is not possible to repel the reconnaissance radar physically, it is always possible to "repel" its radar signals with the aid of jamming/interference.
If it is assumed that a reconnaissance radar with high power output, large antenna gain and low antenna aide lobe levels is used, a commonly applied method of jamming, which reduces the range of an individual such reconnaissance radar, is to make use of a suitably located jammer unit. Such a jammer unit transmits noise interference for example with high antenna gain/high power output around the active transmitting frequency of the reconnaissance radar. Since the transmitting lobe of the jammer must be narrow in order for the antenna gain to be sufficiently great, the narrow transmitting lobe of the jammer has to be accurately directed towards the radar to which jamming is to be caused. This jammer can achieve the intended effect even when the side lobes of the reconnaissance radar receive the interference radiation. Jammers of this type are profitable to counteract.
This is an example of how the effect which is desired can only be achieved to a reasonable degree if the action is taken on a favourable and precise occasion and/or from a narrowly defined direction. This in turn requires advanced equipment which is sometimes so costly to purchase and keep in operation that the number is restricted so severely that the equipment must be transported to operational proximity to the area of interest just when the need arises. This means losses of time, transport risks and gaps in the total area of coverage.
The costs of achieveing a definite effect are often very heavily dependent on the distance to the area of action, and this is clearly so in a military context.